PHYSICAL AND CHEMICAL BASIS OF OBTAINING Al2O3-ZrO2 COMPOSITION BY SPRAY THERMOHYDROLYSIS

Abstract

The relevance. Ceramic compositions Al2O3-ZrO2 have high mechanical strength at elevated temperatures, good thermal shock resistance, which makes ZTA ceramics (a combination of aluminum oxide and zirconium dioxide) suitable for various applications with high requirements: in the chemical and petrochemical industries, in the manufacture of catalysts, the manufacture of instruments, in medicine, etc. In recent years, ceramic materials used in additive technologies are also in wide demand. The aim of the research is to identify the physicochemical foundations of Al2O3-ZrO2 composites preparation by spray-thermohydrolysis from organo-mineral solutions of aluminum trichloride and zirconium oxochloride with certain chemical, phase and dispersed compositions. Objects: organo-mineral solutions of aluminum trichloride and zirconium oxochloride, as well as products of their spray thermohydrolysis, formed during the combustion of organo-alcohol solutions in a flame at temperatures above 400 °C. Methods. Size and shape, elemental composition of the obtained products were determined by scanning electron microscope «S-3400N» from «HITACHI», with attachment for X-ray spectral analysis from «Brooker», phase composition – by X-ray diffractometer «XRD 7000» from «Shimadzu», granulometric composition – by the devices of the firm «Malvern» «Mastersizer 2000» and «Zetasizer Nano ZS», thermal transformations of products and starting materials – by the device for synchronous thermal analysis «Jupiter STA 449 C» from «NETZSCH». Results. The features of thermal transformations of aluminum trichloride and zirconium oxochloride (changes in mass, thermal effects, temperatures of hydrolysis, decomposition, crystallization, phase transformations) in the temperature range of 40–1650 °C have been established. It was found that during the thermohydrolysis of binary solutions, such as AlCl3-ZrOCl2, powder particles are formed. The core of the particles consists mainly of hydrolysis products of aluminum chloride, which has a higher hydrolysis rate, mixed oxide Al0,52Zr0,48O1,74, and the shell is made of zirconium oxide. The authors investigated the uniformity of distribution of Al and Zr atoms in powders of oxide compositions. It was found that the non-uniform distribution of Al and Zr atoms in powders of Al2O3-ZrO2 composites is observed only in large particles with sizes of 100 μm and more. It was established that the characteristics of dispersion depend on both the composition of precursors and the introduction of alcohols, the temperature regime of thermohydrolysis. The average particle size of the powders and the range of sizes decrease with increase in concentration, acidification of the precursor, and growth in the temperature of thermohydrolysis.

Keywords

• aluminum oxide
• zirconium dioxide
• ceramic composition
• spray-thermohydrolysis
• production